1. Field of the Invention
The present invention relates to a Micro Electro Mechanical System (MEMS) switch and a method of fabricating the same and, more particularly, to an MEMS switch which can be driven at a low voltage and solve an occurrence of a stiction fail and a method of fabricating the same.
2. Description of the Related Art
Many electronic systems used in a high frequency band have been made subminiature, ultralight, and high-performance. Thus, subminiature micro switches have been widely studied using a new technique called Micro Machining to replace semiconductor switches such as field effect transistors (FETs) or pin diodes used to control signals in such electronic systems.
RF switches of radio frequency (RF) devices using MEMS technology are widely manufactured. The RF switches are devices mainly applied to circuits selecting and transmitting signals and matching impedances in wireless telecommunication terminals and systems in a micro wave band or a millimeter wave band.
U.S. Pat. No. 6,307,169 discloses such a MEMS switch.
The disclosed MEMS switch includes a hinge supporting a membrane type electrode on a substrate. The hinge includes a control electrode connected to the substrate by an anchor, a hinge collar, and a hinge arm set. The control electrode includes a shorting bar that can be separated from and/or connected to the control electrode. In addition, a travel stop is provided between the substrate and the control electrode to prevent a stiction from occurring.
Japanese Publication Pat. No. hei 2001-143595 discloses another example of an MEMS switch.
The disclosed MEMS switch uses a micro plate frame structure suspended on a spring suspension system and is formed on a substrate. The spring suspension system includes an end to which an anchor is adhered and extends substantially orthogonally to a signal line. The micro plate frame includes a short piece opposite to a gap in the signal line, and an electric contact point post is formed on the signal line to form a condenser structure. A selected voltage is applied to the condenser structure so that the condenser structure is pulled toward a lower electrode due to a static electricity.
A MEMS switch as described above uses an electrostatic force. Thus, a drive voltage is great and a stiction phenomenon occurs. In the stiction phenomenon, an unintentional adhesion occurs on a surface of a micro structure, and thus a restoration force fails to overcome a force working on a surface such as a capillary force, a Van der Walls force, an electrostatic force, or the like. As a result, the adhesion permanently occurs.